Pulsing arrangement



M y 1950 J. VAN DER MARK ETAL 2,509,998

PULSING ARRANGEMENT Filed April 26, 1946 INVENTORS. JANVANPBRMRK ADOZPH VENIS GEORGEPFIIIPROSZBACK LAT/KENS 3110K AGENT- Patented May 30, 1950 UNITED sates STATEE ?ATENT .F'FlCE PULSING ARRANGEMENT Application April 26, 1946, Serial No. 665,310 In the Netherlands March 13, 1942 Section 1, Public Law 690, August 8, 1946 Patent expires March 13, 1962 Claims.

In practice it is frequently desirable that a circuit arrangement should be available which on the arrival of a signal with very small time lag produces a sudden single or pulse-like variation in current or in voltage: for example for the sudden release, permanent or shortlived respectively, of a cathode ray beam of a cathode ray oscillograph for enabling single phenomena to be observed.

In this case the time interval which elapses between the arrival of the signal, in the present case the single phenomenon to be recorded, and the release of the cathode ray beam, which time interval is sometimes referred to as the switching time, should be a minimum in order that as little as possible of the phenomenon to be observed becomes lost. In this connection it is to be taken into account that the time interval within which the sudden variation in current or voltage has itself to take place in the circuit arrangement necessary for setting up thereof should be materially shorter than the desired switching time because for example the impedances of the connecting leads between the circuit for setting up the variation in current of voltage and the cathode ray oscillograph bring about an unavoidable time lag, or in other words an undesired decrease of the flank steepness of the switching voltage. The flank steepness of the switching voltage generated and also its amplitude should therefore have a maximum value.

In a cathode ray oscillograph for enabling single phenomena to be observed it is known to obtain the switching voltage required for the sudden release of the cathode ray beam from a screen grid valve connected as a dynatron. The flank steepness and also the amplitude of the switching voltage set up by means of this well-known device is. however, comparatively small. A further disadvantage is the high hysteretic shape of the dynatron characteristic curve.

For many purposes it is also desirable to generate pulse-like oscillations. Such oscillations are used for example in television devices for disrupting the cathode ray beam in a cathode ray tube during the striking back time. Pulse-like oscillations are also frequently used for measuring practice, for example in devices comprising a cathode ray oscillcgraph for enabling a plurality of phenomena to be observed simultaneously, the phenomena being in succession fed in quick sequence to the oscillograph by means of discharge paths used as inertialess switches (for example diodes or amplifier valves) and rendered operative in turn by means of the pulse-like oscillations serving as a switching voltage.

In known devices of the last-mentioned kind the required switching voltage is frequently obtained from a multivibrator circuit arrangement comprising two amplifying valves cascade or push-pull connected.

In this case also it is generally favourable if flank steepness and amplitude of the pulse-like oscillations are very high.

The invention has for its object to provide a circuit arrangement permitting of generating single or pulse-like current or voltage variations or else pulse-like oscillations having particularly high flank steepness and amplitude.

A circuit arrangement according to the invention comprises a secondary emission valve whose control grid circuit and auxiliary cathode circuit impedances are each substantially formed by ohmic resistances and in which the control grid circuit and the auxiliary cathode circuit are coupled regeneratively, the value of the auxiliary cathode circuit resistance and the strength of the coupling being chosen to be such that only by means of control grid voltages which are lower than a first limit value (at which the anode current at least has a given value) or are higher than a second larger limit value (at which the anode current is at least substantially suppressed) a stable operating point of the value can be acljusted.

In order that the invention may be clearly understood and readily carried into effect it will now be described more fully with reference to the accompanying drawing, in which favourable practical forms of the circuit arrangement according to the invention and two graphs are i1- lustrated.

Fig. 1 shows a circuit arrangement according to the invention by reference to which the operation will be set out.

Figs. 2 and 3 show control grid voltage-anode current characteristic curves to elucidate the operation of the circuit arrangement shown in Fig. 1.

Fig. 4 shows a circuit arrangement for setting up a single variation in current or voltage.

Fig. 5 shows a circuit arrangement for setting up a pulse-like current or voltage variation upon the arrival of a signal of given polarity.

Fig. 6 shows a circuit arrangement responsive to a signal of any polarity.

Fig. 7 shows a circuit arrangement for setting up pulse-like oscillations, and

Fig. 8 shows a circuit arrangement in which various measures are taken to shorten the switching time.

In the figures like parts are designated by similar reference numerals.

Referring to Fig. l in which the circuit arrangement according to the invention is illustrated in a very simple executional form, I designates a secondary emission valve comprising a cathode 2, a control grid 3, a secondary electron emitting electrode or auxiliary cathode 4 and an anode 5. The anode and auxiliary cathode voltage of the valve is obtained from two series-connected batteries 5, 'I, the negative terminal of the battery 6 being connected directly to the cathode 2 the point of connection between the batteries 6' and 1 via an ohmic resistance 8 to the auxiliary cathode l and the positive terminal of the battery '5 via an ammeter 9 and an ohmic resistance It to the anode 5 of the valve. The auxiliary cathode I and the cathode 2 have interconnected between them the series combination of an ohmic resistance II and a battery I2 with adjustable terminal voltage, whereas control grid 3 is connected to a variable tapping point 53 of the resistance I I. The positive terminal of the battery I2 is connected to the cathode 2 and the negative terminal to the resistance I I. The part of the resistance I I which is comprised between battery I2 and tapping point I3 forms part of the control grid circuit of the valve. Thus a control grid bias is derived from the battery I 2 and the voltage between: control grid and cathode of the valve i. e. control grid voltage corresponds with the differ ence between the bias of the battery I2 and the oppositely directed voltage at the part of the resistance I! which is comprised between battery IZ and. tapping point I3.

Before entering into the details of the prop ertiesof the circuit illustrated it must be premised that the supply voltages and the resistances are chosen to be such that, as is common practice with secondary emission valves, the flow of primary electrons is always smaller than the consequent fiow of secondary electrons and an increase in the flow of primary electrons always brings about an increase in the flow of secondary electrons passing between the auxiliary cathode and the anode.

If in the circuit arrangement illustrated the tapping point I3 is displaced at least substantially wholly downwards so that the control grid voltage practically corresponds at any one time with the voltage 'of the battery I2, a stable operating point of the valve always will be obtained, in the case of" variation in the voltage of the batteries between for example 30 volts and 0 volt, in conformity with the relation, shown in Fig. 2 .by the curve A, between control grid voltage e and the anode current ie of the valve which is determined byineans of the ammeter 9.

If the anode current is approximately suppressed the auxiliary cathode voltage practically corresponds with the voltage of the battery 6; the auxiliarycathode voltage, however, increases with the anode current la due to the voltage brought about across the resistance 8 by'the aux-- iliary cathode current. The increase in the auxiliary cathode voltage will also result in an increase in the current passing through the resistance *II but with a tapping point I3 displaced completely downwards this does not bring about any alteration of the control grid voltage.

If the tapping point It is displaced in an upward direction so that the part of the resistance II comprised between the tapping point It and the battery I2 forms part of the control grid circuit, an increase in the auxiliary cathode potential will also resultinv an increase in the control grid potential or alternatively a decrease in the (absolute value of the) control. grid voltage. This then occurring regenerative coupling brought about by the negative steepness of the control grid voltage-auxiliary cathode current characteristic curve will be stronger as the tapping point 13 is more displaced in an upward direction.

it has now been found that at a given strength of the regenerative coupling between control grid and auxiliary cathode circuits in the circuit arrangement illustrated the relation between con trol grid voltage and anode current as designated by the curve B of Fig. 3 occurs, it being only possible by means of a control grid voltage which is lower than the first limit value I or higher than the second, larger, limit value II to adjust a stable operating point of the valve. For any value of the control grid voltage comprised between these two limit values, a stable operating point is not obtained, as is designated b the dotted part of the curve B. If, for example, the control grid voltage is initially lower than the limit value I, at which the anode current has a given, comparatively larger value and the battery voltage I2 is increased, as soon as the control grid voltage exceeds the limit value I the latter will, due tc the regenerative coupling, spontaneously assume the limit value II, at which the anode currentfis suppressed at least substantially. With a further increase in the battery voltage the control grid voltage increases and the anode current still decreases slightly but the then adjusted operating point is stable as result of the then occurring very low negative steepness of the control grid voltage-auxiliary cathode current characteristic curve. thatthe operating point adjusted atcontro-l grid voltages lower than the limit value I would be unstable if the grid current which occurs at these control grid voltages and which counteracts a reduction in the grid current voltage had not a stabilizing efiect. The more the grid current circuit resistance is increased, as may be ensured for example by means of a resistance interconnected between the control grid and the tapping point I3, the stronger is the said stabilizing effect.

If, starting with a control grid voltage having a higher value than the limit value II, the battery voltage I2 is decreased, the anode current, upon exceeding the limit value II in the direction of the limit value I, will spontaneously assume and retain a value corresponding to the limit value I until for any reason the control grid voltage exceeds the limit value I with the result that the operating point of the valve again shiftsto II.

This shifting or leaping oi the operating point from. I to II or vice versa, ensues very quickly and the anode current variation is very large. In the condition II the anode current is substantially suppressed, whereas in condition I approximately the anode current normally occurring at a control grid voltage of 0 volt, which with a secondary emission valve of the type EE50 in the circuit arrangement shown is about 25 ma, passes.

- The time period for the leaping of the operating point from I to II or vice versa is dependent on various factors. This time period is lower, as the negative steepness of the control grid voltageauxiliary cathode current characteristic curve is increased, said steepness being, as is well-known,

It must be observed even with the secondary emission valves actually in use particularly great.

If in the circuit arrangement according to the invention use is made Of amplifier valves comprising several cascade-connected auxiliary cath odes (electron multiplicator) it is possible to obtain an even greater negative steepness.

The use of a very strong regenerative coupling between control grid and auxiliary cathode circuits also permits of decreasing the said time period; the coupling may, for example, be in creased by connecting a condenser between auxiliary cathode and control grid so that a particularly strong coupling is provided for alternating voltages which are responsible for the leaping of the operating point.

An increase of the resistance 3 in the auxiliary cathode circuit has a similar effect but it is advantageous if in the conductive condition of the circuit arrangement (limit value I) the auxiliary cathode potential is so much lower than the anode potential that the steepness of the control grid voltage-auxiliary cathode voltage characteristic curve at the then obtaining operating point is still so negative that the operatin point is only stable due to a secondary effect since otherwise the said time period increases. It must be remarked that if the auxiliary cathode resistance is further increased the regenerative coupling which brings about a particularly quick leaping of the operating point when the circuit arrangement is in the conductive condition becomes a degenerative coupling for this condition due to the positive steepness of the control grid voltageauxiliary cathode current characteristic curve at the operating point then obtaining and thus stable without any secondary effect.

Further shortening of the said time period may be ensured by suitably constructing the circuit arrangement in a manner poor in capacity, to which the circuit arrangement according to the invention lends itself particularly thanks to the great simplicity. Finally, quick leaping of the operating point may be assisted by taking care that when the control grid voltage corresponding to one of the limit values I, II is even very slightly exceeded in the direction of the other limit value the then eifective negative steepness has a maximum value. The measures advisable for this purpose will be set out by reference to the circuit arrangement illustrated in Fig. 8.

In the circuit arrangement shown in Fig. 1 the variation in steepness for a given low variation in grid voltage is larger than I than with II so that the leaping from I to II takes place more rapidly than from H to I.

The practical form of the circuit arrangement according to the invention shown in Fig. 4 essentially corresponds to that shown in Fig. 1 but in this case the auxiliary cathode and anode voltage is obtained from a single common source of voltage, for example rectifier apparatus. The auxiliary cathode 4 is connected on the one hand via a resistance 14 to the positive terminal of the common source of anode voltage not shown whose negative terminal I 5 is earthed. On the other hand the auxiliary cathode 4 is connected via a potentiometer constituted by resistances IS, IT and corresponding to II of Fig. 1 to the negative terminal of the bias battery. The control grid is connected to the point of connection of the resistances I6, I! and via condenser N3 of preferably very low capacity to one of the input terminals I 9. The other input terminal is earthed, as is also the cathode 2 of the tube. The anode of the tube is also connected to the positive terminal l5 via an anode resistance Ill. The ends of the anode resistance I0 are connected respectively to the output terminals 20.

If, by means of the battery I2, such a grid bias is adjusted, that the control grid voltage corresponds to the limit value I or II the operating point of the valve I will (if a voltage pulse 2| of suitable polarity is fed to the input terminals) leap from the valve l to II or vice versa with the result that a single sudden voltage variation can be derived from the output terminals.

This potential variation may be utilized for example for the sudden suppression of the disruption of the cathode ray beam of an oscillograph. It has been found that the time that elapses between the arrival of the input signal 2| and the release of the oscillograph (switching time) can be limited to about 10-- second.

It must be remarked that the input signal cannot only be fed to the control grid but obviously also to the auxiliary cathode or to the cathode (vide for example Fig. 6).

The circuit arrangement shown in Fig. 5 is adapted for the generation of a double pulse like potential variation on the arrival of a signal of suitable polarity.

This circuit arrangement is differentiated from that shown in Fig. 4 in that the part of the potentiometer which is comprised between auxiliary cathode 4 and control grid 3 is formed by a condenser 22 and the auxiliary cathode is connected via the auxiliary cathode resistance 8 to the point of connection between the resistance l4 and a resistance 23, said resistances constituting a low ohmic potentiometer connected in parallel with the source of anode voltage.

Thus, if the operating point of the tube that corresponds to I is adjusted the operating point of the tube will leap to II.

Thus, if the operating point of the tube that corresponds to I is adjusted the operating point of the tube will leap to II if the voltage pulse of negative polarity is fed to the input terminals l 9 but, after a lapse of the time period governed by the RC time of the circuit arrangement and required for the charging of the condenser 22, will spontaneously leap back to I so that the initially occurring anode current is first suddenly suppressed and eventually, suddenly starts to flow again with the original strength. Thus, on the arrival of the signal a pulse-like voltage may be obtained from the output terminals 20 and this voltage may be utilized for example for the transient release or disruption of an oscillograph.

If the operating point corresponding with II is adjusted a pulse-like voltage will occur at the output terminals 20 if a signal of positive polarity is fed to the input terminals.

With this circuit arrangement also it may be advisable to use a mixed coupling that is to say a capacitative and in addition a galvanic coupling between control grid and auxiliary cathode circuits. In this case the galvanic coupling should, however, be comparatively feeble to prevent the operating point prevailing during the charging or discharging of the condenser 22 from being maintained even subsequently to that so that a single instead of a pulse-like potential var iation occurs at the output terminals.

The circuit arrangement illustrated in Figs. 4 and 5 are only responsive to an output signal of predetermined polarity, said polarity being dependent on the operating point chosen for the circuit arrangement in the awaiting condition.

Frequently, however, :it .is desirable that the circuit'arrangement: should: beresponsive to a signal of any polarity'and this can be ensured by the use of the circuit arrangement shownin Fig. 6.

'Inthis' circuit arrangement, which depending on the proportioning may serve to generate either a single or a pulse-like potential Variation, aportion 2% of the control grid circuit resistance 24,25 is included in thecathode lead of the valve I and control grid and cathodeare connected respectively via oppositely connected diode rectifiers 26, Zltothelinput terminal E9 not earthed.

Thus,.ifithe-operatingpoint of the valve that corresponds' to I is adjusted it will leap immediately on thearrival of the signal irrespective of the=polarity of thelattenas will be clearly evident. In View of the negative feedback coupling brought about by the resistance at it is advisable to choosethe regenerative coupling stronger than in the case ofthe foregoing circuit arrangements.

Circuit arrangements according to the inventionmay also be used for generating pulse-like oscillations. In the circuit arrangement therefor shown in Fig. 7 the regenerative coupling be tween control grid and auxiliary cathode circuits, which should be at least preponderantly capacitative, is solely capacitative and the voltage of thebattery I2 is so adjusted that irrespective of whether the operating point I or II obtains the control grid voltage eventually approaches a valuewhich-is comprised between the values corresponding to the operating points I and II. In this case the generated pulse-like oscillations may be obtained from the output terminals 20, as is denoted in the figure at28. The generated oscil- :1:

lations may be synchronised by synchronising pulses 29 fed to the control grid via the input terminals [9. It should be mentioned that similarly to'the circuit arrangements shown in the foregoing figures the output impedance may be inserted not only in the anode lead of the tube butalso for example in the cathode lead or alternatively it may form the resistance M or part thereof. Generally, however, preference should be given to the circuit arrangement illustrated.

As alreadyobserved in the foregoin it is desirable for the obtainment of as quick a leaping as possible of the operating point from I to 11 or vice versa that the operative steepness adjacent the limit value I and II varies as intensely as possible.

To the circuit arrangement shown in Fig. 8 useis made of two measures therefor which may successfully be employed with all the circuit arrangements set out hereinbefore.

In this case, the control grid 3 and the cathode 2 have interconnected between them the series combination of a diode and a battery 3!. The cathode of the diode is connected to the negative terminal of the battery 3! and thus exhibits a potential, which is negative relatively to the cathode 2 of the valve l; the diode-anode is connected to the control grid 3 of the valve 5. The control grid voltage is thus prevented from falling below a limit value governed by the voltage of the battery 22 and designated I in Fig. 3. Due to this the operating point of the valve in the conductive condition becomes stable even at the limit value I of the control grid voltage instead of only at II due to the grid current. Since the diode characteristic curve manifests an intenser ourvation near the zero point than the corresponding grid cathode characteristic curve of the valve 1 the variation of the efiective steepness at the limit value I' for the characteristic curve designated (tin Fig. 3 and obtainingffor the circuit arrangement shown in Fig. 8 exceeds 'that'at the limit value I in the foregoing circuit arrangements. Due to this the operating point will leap particularly quickly from I to II so that if very quick response of the circuit arrangement to an incoming signal is required preferably the operating point corresponding to the limit value I is adjusted.

The limit value II in Fig. 3 can be shifted to the right in a similar manner.

A similar effect for the part of the characteristic curve which is located in the neighbourhood of the limit value II is obtained by interconnecting a voltage-constant resistance, for example a glow discharge tube '32, between the resistances M and 23 in the manner shown in Fig. 8. This measure also permits of limiting the load of the source of anode voltage. In order that in the foregoing circuit arrangements, the auxiliary cathode voltage may have a favourable value both at limit value I and II, the current passing through the potentiometer connected in parallel with the source of anode voltage (for example I i, 25 in Fig. 6)--from which theauxiliary cathode voltage is derivedshould as a matter of fact be considerably larger than the auxiliary cathode current. The use of the glow discharge tube 32 ensures that with suppressed anode'current of the valve i the auxiliary cathode voltage does not fall below a value governed by the voltage at the glow discharge tube 32 and the battery [2.

As mentioned before, the circuit arrangement according to the invention may be used with ad vantage with oscillographs for the sudden release and/or disruption of the cathode ray beam. The generated sudden variations in the current or voltage may also be used'for causing a saw tooth generator supplying the time base voltageofthe oscillograph to become operative. 'Itis, however,

also 'possibleto obtain a time base'voltage'from the circuit arrangement according'to the invention viz. by connecting a condenser 33 '(Fig. 8) in parallel with the output impedance, i. e. with the anode resistance It or in parallel with part thereof. In this case the occurrenceof a sudden variation in the anode current will result in the occurrence at the condenser of a voltage gradually increasing (or decreasing respectively) in the course of time which may be used for example as a time base voltage with oscillographic recording of single phenomena.

We claim:

1. In a circuit arrangement for generating a sudden impulse in responseto aninput voltage, the combination comprising an electron discharge tube having a cathode, a control grid, an auxiliary electrode emitting secondary'electrons upon the flow thereto of primary electrons fromthe cathodeand an anode, first and second impedance eiements, a source of operating potential having its negative terminal connected to Sal-f1 cathode and its positiveterm nal connected through said first element to said auxiliary electrode and through said second elementtc said anode. means regeneratively coupling auxiliary electrode to said grid, a source of bias potential having its positive terminal connected to said cathode and its negative terminal VG grid, voltage responsive means connected between said grid and said cathode arranged to prevent the voltage the grid from falling below a predetermined value, and means to "apply an input voltage to said grid causing a sudden impulse to be developed across said second element.

2. In a circuit arrangement for generating a sudden impulse in response to an input voltage, the combination comprising an electron discharge tube having a cathode, a control grid, an auxiliary electrode emitting secondary electrons upon the flow thereto of primary electrons from the cathode and an anode, first and second impedance elements, a source of operating potential having its negative terminal connected to said cathode and its positive terminal connected through said first element to said auxiliary electrode and through said second element to said anode, means regeneratively coupling said auxiliary electrode to said grid, a source of bias potential having its positive terminal connected to said cathode and its negative terminal connected to said grid, voltage responsive means connected between said grid and said cathode and arranged to prevent the voltage on the grid from falling below a predetermined value, said voltage responsive means including a unidirectional rectifier connected in series with an auxiliary potential source, said predetermined value depending on the magnitude of said auxiliary source and means to apply an input voltage to said grid causing a sudden impulse to be developed across said second element.

3. In a circuit arrangement for generating a sudden impulse in response to an input voltage, the combination comprising an electron discharge tube having a cathode, a control grid, an auxiliary electrode emitting secondary electrons upon the fiow thereto of primary electrons from the cathode and an anode, first and second impedance elements, a source of operating potential I having its negative terminal connected to said cathode and its positive terminal connected through said first element to said auxiliary electrode and through said second element to said anode, means regeneratively coupling said auxiliary electrode to said grid, a source of bias potential having its positive terminal connected to said cathode and its negative terminal connected to said grid, voltage responsive means connected between said grid and said cathode and arranged to prevent the voltage on the grid from falling below a predetermined value, said voltage responsive means including a diode device having an anode and a cathode, and an auxiliary potential source, the anode of said device being connected to the grid of said tube, the cathode of said device being connected to the negative terminal of said auxiliary source and the positive terminal of said auxiliary source being connected to the cathode of said tube, said predetermined value depending on the magnitude of said auxiliary source and means to apply an input voltage to said grid causing a sudden impulse to be developed across said second impedance.

4. In a circuit arrangement for generating a sawtooth pulse in response to an input voltage, the combination comprising an electron discharge tube having a cathode, a control grid, an auxiliary electrode emitting secondary electron upon the flow thereto of primary electrons from the oathode and an anode, first and second impedance elements, a source of operating potential having its negative terminal connected to said cathode and its positive terminal connected through said first element to said auxiliary electrode and through said second element to said anode, a first capacitor connected between said auxiliary electrode and said grid to provide regeneration therebetween, a source of bias potential having its positive terminal connected to said cathode and its negative terminal connected to said grid, a diode rectifier having an anode connected to said grid and a cathode, an auxiliary potential source having its negative terminal connected to the oathode of said diode and its positive terminal connected to the cathode of said tube, said rectifier acting to prevent the voltage on said grid from falling below a level depending on the magnitude of said auxiliary source a second capacitor connected across said second element, and means to apply an input voltage to said grid causing a sawtooth pulse to be developed across said second element.

5. In a circuit arrangement for generating a sudden impulse in response to an input voltage, the combination comprising an electron discharge tube having a cathode, a control grid, an auxiliary electrode emitting secondary electrons upon the flow thereto of primary electrons from the oath-- ode and an anode, first and second impedance elements, a source of operating potential having its negative terminal connected to said cathode and its positive terminal connected through said first element to said auxiliary electrode and through said second element to said anode, a capacitor connected between said auxiliary electrode and said grid to provide regeneration therebetween, a source of bias potential having its positive terminal connected to said cathode and its negative terminal connected to said grid, a diode rectifier having an anode connected to said grid and a cathode, an auxiliary potential source having its negative terminal connected to the cathode of said diode and its positive terminal connected to the cathode of said tube whereby the voltage on said grid cannot exceed a predetermined value, a voltage regulating gaseous discharge device connected between said grid and a point in said first element, and means to apply an input voltage to said grid causing an impulse to be developed across said second element.

JAN VAN DER MARK.

ADOLPH VENIS.

GEORGE PHILIP ROSZBACH. LAURENS BLOK.

REFERENCES CITED The following references are of record in the file of this patent:

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